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UNITED STATES PATENT OFFICE.

WILLIS AFGI BBONS, OF NEWYORK, AND HERMAN W. BITTER, OF BROOKLYN, NEW YORK, ASSIGNORS TO AMERICAN RUBBER COMPANY, A CORPORATION OF MASSA-E GHUSETTS.

PERMEABLE SHEET 1,427,754. No Drawing. Application To all whom it may concern:

Be it known that we, WILLIs A. GI oNs and HERMAN lV.:RiT'rEn, both citizens of the United States, residing at New York, county and State of New .York, and ,Brooklyn, county of Kings, and State of New York, respectively, have invented certain new and useful Improvements in Permeable Sheet Materials and Processes of Making Same, of which the following is a full, clear, and exact description.

Artificial or imitation leathers have here tofore been made in three general ways; first by coating a fabric backing with nitrocellulose composition, second by coating it with a rubber composition, and third, by coating it with a mixture of oxidized or polymerized oil suitably compounded. The pliability and weather resisting characterof the rubber type has marked advantages over the others. But the rubber composition as jwell as the other types mentioned have all been unsuitable for wearing apparel, up holstery and like uses on account of their inability to breathe after the fashion of leather. None of the prior imitations permitted the escape of water vapor or air and the dissipation of heat so as to afford relief to a wearer of articles made therefrom.

This invention aims to provide a permeable sheet material of plastic composition (preferably but not necessarily of vulcanizable rubber composition) that is pliable and porous or transpiratory. and to degree if desired even greater than leather.

the physical properties of the leather which it is intended to supplant. It also aims to provide such permeable sheetmaterial that does not absorb water in liquid form ap preciably, whereas leather will get'wet or water-soaked. Thecinvention further aims to provide a commercially practical method ties, that yields a product of uniform qual ity and any desired porosity,that readily permits dressing or desirably forming the surface of the finished sheet in imitationof many varieties of leather, and finally,'that'is applicable to a variety of plastic compositions.

With the specific details of the invention in mind and without intention to limit its Applied to a backing, it may have substantially MATERIAL AND PROCESS OF MAKING SAME.

Specification of Letters Patent. Patented A11 29, 1922.

filed March 31, 1921. Serial No. 457,502. I

scope more than is required by the prior art, the invention may be said to consist in the discovery that fluidin general and waterin particular may bedistributively incorporated in plastic compositions and, after sheeting, but before complete or final set of'the plastic mix, may be expelled so as to leave minute poresor openings through the composition which. may be permanently retained by the complete setting of the plastic in ,a pliablesheet form.

The invention has been extensively exploited, and the procedure followed with different. compounds will now be detailed.

A compound of the following substances by way of example Pale crepe 100 Zinc oxide 1O Para toluidine l Sulphur 2 Dibutyldixanthicdisulphide 4 be batched on a mill iii-the usual man- .ner and there combined with a quantity of but not so soft that it cannot be stripped from the batch facilitating incorporation of the wet fibers. In this operation more or less water is squeezed out. The retainedwater constituting a blowing agent incidentally stiffens the batch somwhat and renders it "naphtha or after the incorporation of water and complete mix of the 'batch ready for calendering or otherwise sheeting.

less tacky or, sticky which is desirable of i are exposed.

The next step is to sheet the mix, This may be conveniently done on a calender whose rolls are preferably in this case at least about or slightly above room temperature depending upon the consistency of the batch; And preferably but not necessarily the mix is calendered onto a fabric backing that has previously been thinly coated by spreading or frictioning with a rubber composition of high quality.

Then desirably but not necessarily the calendered sheet may be embossed and varnished or otherwise dressed with or without apreliminary short cure. Likewise optionally, it may be surfaced by spreading in a well known manner with nitrocellulose.

The next step is to expel fiuid in the aeriform state and the final step is to set the sheet in its porous condition and serviceably permanent. In the instant case, the curatives being rapid, i. e. requiring only ten to thirty minutes heat at 200 F. (or a longer time at a lower temperature), these steps are accomplished successively in the curing, at the initial and final stages respectively of the heat treatment. The sheet may be cured either in the condition it comes from the calender or after embossing or dressing its surface. The curing may be effected in a wide variety of ways known to the trade, hanging in heated ovens or chambers similar to those employed in the shoe industry being very satisfactory. The temperature and duration of the cure 'depend upon the curatives employed and the presence or absence of an accelerator, in the instant case twenty to thirty minutes at a rising temperature to 200 F.

During the first few m nutes of the cure .in the given case the softening action of the solvent naphtha increases with the rise in temperature, and the water is converted into vapor and expelled as the temperature increasesits pressure. Very largely it is thought the vapor follows the path of least resistance afforded by thefibers whose ends To secure uniformity in the physical condition of the product, the sheet should remain sufficiently soft during sayfthe ffirst tenminutes of the cure as to permit a large portion of the water passing off in the form of yapor but the period will vary with the composition. A too powerfulcuring ingredient or a too high vu'lcanizing temperature is liable to Caseharden the 'sur face by forming a skin of partially cured rnbberwhich of course would prevent the uniform exit of thewater vapor and thereby develop blisters and a non-uniform appearance in the product. After vulcanization if desired, the material may be dressed with suitable varnish or the like, ifnot already so. Finishingbefore final setting is however deemed' 'iirefera'ble, one advantage being that the embossed design then stands out more distinctly or sharply, and another advantage being that sticking of upholstery stocks for instance is prevented during calring W If the product desired is relatively thln, dry fibers may be used instead of wet fibers and air entrapped in their mixture'r'elied upon to yield porosity. In such cases, however, the mix is liable to stick to the calender rolls and great care must be taken in its manipulation. The use of dry fibers on the mill does not now appear to be a desirable course as uniform porosity in the product's seems somewhat uncertain.

The mixing of the ingredients in prepara tion for calendering or sheeting may be accomplished variously.

' One modification consists in mixing the color and such curati'ves as practicable with the rubber on the mill andthen mixing in ground rags either simultaneously with or prior to the addition of the solvent naphtha. After the rags have been mixed dry and the naphtha has been combined with the rubber. water may be added either in predetermined amount or in excess, in which latter case it is removed by refining or by expressing in a bag. If powerful curatives or accelerators either ground or the grinding effected by'-- the 'vi'go'rous action of the mill rolls. This batch may now be put into a mixer of any suitable kind, such as the well-known Werner "& Pfieide'rer type having curved blades revolving in a closed casing, and in the n'ixercom'bined with solvent naphtha. When the batch in the mixer has been worked to a smooth and uniform dougha measured quantity'of water shou'ld be added. Powerful accelerators, if used, should be addedafte'rthe naphtha or even'after the water. The quantity of water will vary with the compound employed and especially the quantity of fibers. But the following "may be taken as an example of suitable proportions of the ingredients Pale crepe 100 Zinc oxide 10 (Para toluidine 4 Sulphur 3 Ground-rag 85 Dibutyldixanthicdisulphide 5 Solvent naphtha 75 Water 85 It has been found that the ground rag need not be incorporated with the batch on the mill but that it may be worked in in the.

mixer, which is a further alternative way of making up the batch. After the rubber,

minerals, curatives and colors have been batched on the mill they may be removed.

and put into a mixer together with solvent naphtha and ground fiber. They may then be worked until a substantially uniform dough is obtained. A measured quantity of water-say 7 5 parts-maythen be added,

and the mixlng continued until it has been tribute the fluid and fibers in the plastic may be widely varied.

It does not seemto be essential to follow any particular order in adding the ingredients and satisfactory re sults may be variously obtained, except that in quantity production at the factory powerfulcuratives and accelerators can be handled or incorporated with less danger after the rubber has been softened with solvent naphtha or after complete. mixing and preliminary to sheeting. Vigorous kneading by machines such as mixing mills or mixers would otherwise be likely to cause premature or partial vulcanization.

In the foregoing examples so-called quick curatives were employed these having the desirable property of completely vulcanizing in say ten .to thirty minutes at a temperature of 200 F., or less, which is of course commercially advantageous. But the invention is not limited to the use of such quick curatives and is applicable to ordinary volcanizable rubber compositions. The following:

Pale crepe"; 100 Lamp black 20 Litharge 30 Solvent naphtha"; u Sulphur Ground rags ("wet)l l l 8 5 may be employed to produce a porous sheet material. lVith such materials the procedure is to, blend the ingredients on a mill, to then soften with solvent naphtha, and finally to add fibers and water according to the principles alreadyoutlined. The mix may be calendered alone or onto fabric and suitably cured in an oven for instance at a temperature of 270 lifor 4% hours.

It has also been discovered that a sheet calendered or otherwise made from a batch of the composition of the first example but without incorporated water may have the poreproducing liquid introduced by soaking in warm water for example for about hour. During theinitial stages ofits cure or set porosity is developed but not as uniformly as desirable. This method is not deemed desirable but is comprehended in the broad invention.

It seems therefore that the invention is applicable to vulcanizable rubber compositions generally and that the temperature and duration of cure may be varied widely to suit the composition selected.

Instead of vulcanizable rubber, nitrocellulose may be employed as the fiber binder. The following Pyroxlyin 12 grams. Castor oil l2 Cotton fibers (wet) 10 Amyl acetate 200 cc. Benzol 125 0.0. Carbon black; 1 gram.

maybe made into a porous imitation leather.

The pyroxylin and castor oil may be dissolved in amyl acetate and thinned with benzol to a relatively fluid consistency and the wet fibers stirred in. The mix may then be spread on fabric with a knife or spreading machine and driedbetween coats at a temperature of approximately C., ast

many as twenty-five coats being applied if desired. 1

In this connection it is noted that nitrocellulose may be blended with a vulcanizable rubber composition and so as'to. extend throughout the thickness of the sheet, or as an intermediate coat between the plastic base and the finished surface or asa finishing coat on the rubber alone or blended. With upholstery where a surface not frictionally opposing sliding contact is desirable, a cellulosic surface dressing is of advantage.

A permeable-sheet material may be produced by incorporating gas. This has been mentioned alread in the making of a very thin sheet, it having been found possible to entrap air with dry fibers into the naphtha softened plastic on the mill. 1 But as before intimated, this procedure does not yield uni satisfactory results with air or gas may be obtained with the plastic or vulcanizable rubber of a fluid like consistency permitting the fibers (either wet or dry, but the former preferably), to be stirred thereinto. The air or gas in this'case isentrapped with the fibers during the stirring operation. If desired, the, air entrapped with the fibers may be augmented by blowing or otherwise disseminating free air into the mixture. Or the entrapped air maybe supplemented by in eluding in the compound light, air-occlusive materials, such as magnesiumcarbonate, approximating the weight of fibers Q employed, which latter by weight, preferably approximate the amount of rubber in the cement. The more or less fluid batch obtained may be sheeted as desired with a kn fe or on a spreading machine having a steam chest in rear of its immersion rolls on which chest the sheet may be passed and dried so as to If vulcanizable, the

leave the sheet porous. sheet is then preferably, but notnecessarily, subjected to a vulcanizing heat.

The product of all the various methods above outlined is a transpiratory or air-permeable sheet material freely flexible and in most cases having the appearance and feel of leather, and substantially its resistance to abrasive scuffing. It will not absorb water to an objectionable extent and ordinarily hardly to an appreciable extent depending of course upon the diameter of the pores. Its heretofore-unattainable-property of passing air or water vapors renders it practical as a substitute for leather, and therefore adaptable for articles of wearing apparel to a degree not attained by its predecessors. The porosity, transpiration, or air-permeability (however its breathing quality may 1 be termed) is believed to be due to the expulsion of aeriform fluid (vapors of the .Water or mingled vapors of solvent and air or other gas, or of the air or gas alone) prior to the complete setting of the material in a permanent serviceable condition. The expulsion occurs before set or vulcanization has reached the stage of sealing off or case hardening the surface of the sheet. The pores or openings are minute, being scarcely visible, but they impart to the finished sheet the appearance and feel of leather, giving as it were a grain. By suitable embossing the material may be made in imitation of almost any variety of leather.

If the proportion of fibers is varied, the physical appearance of the material may be altered. Insole stock for instance, more nearly resembling felted materials than leather, can be made from Parts. Pale crepe 100 Zinc oxide '30 Sulphur l 1 Tribenzyltrimethylenetriamine 3 Dibutyldixanthicdisulphide- 5 Ground rags 150 WVater u 75 Solvent naphtha 7 5 Instead of tribenzyltrimethylenetriamine in the above formula, aniline in the same proportion may be employed as an accelerator, where it has no intolerable effect on the colors employed. The materials may be compounded on a mill or mixer, then sheeted on a calender according to the steps first detailed, and cured in twenty to thirty minutes at a rising temperature to200 F.

Taking calf-skin as, a standard, and as- .nezmse suming its transpiration or air permeability is 100, sheet material made byincor'porating a gas or air has been obtained with a transpiration substantially. as high as leather.

IVithwater incorporated to blow or produce pores, a transpiration of 200' or even higher may be obtained. vT'ests for trans piration may be made by placing water in a container with the material covering the mouth and above the surface of the Water, the marginsbeing hermetically sealed. The container may then be allowed to stand for twenty-four hours at a temperature of about 20 C. The loss in'weight'due to the passage of water .vapor out through the material to the exterior forms a basis of comparison with leather which had been subj ec'ted to the same treatment.

In the basic or broad process the first common step is to mix filler and plastic materials and distributively incorporate fluid therein. The preferred procedure is to mix the ingredients on a mill or in a mixer or both and to incorporate water as the blowmg agency. Such a course is more prac .tical at the factory, yields a uniform product for any selected composition, and requires the least expense. The batch may be thus prepared in a. calenderable condition and calendered in sheet form alone or onto either a permanent or a temporary backing and the pro'cedure is feasible for themanu- .fact-ure. of insole material where there is a large field for its use. WVater hitherto regarded intolerable acts with surprising excellence as a pore producing agency. It is cheap. available, and reliable, and permits embossing or dressing the surface of the sheet stock before vulcanization or before complete setting in a wider variety of ways without danger of altering the porosity, which property in its use, is not developed until the sheet is subjected to heat. Where composition but also through the surface dressings, the sheet being porous'or permeable through and through.

The second general step in the method, to Wit, sheeting the mix, comprehends rolling or spreading the plastic (with a calender or a spreading machine), and in the former case at least eitheralone or onto a fabric backing or onto a temporary backing that is subsequently stripped. Insole stock, for instance, is preferably or rather more cheaply made without a backing. Imitation leathers, on the other hand, desirably have tensile strength approximating if not equal ing or surpassing the particular leather to be supplanted and are preferably made by applying the mix to a fabric backing of appropriate strength and texture. And while it is preferred to apply the mix to only one side of the fabric, both sides of the fabric may be coated. Calendering is of course preferred to spreading but thelatter has limited fields of usefulness. l

The next step, expelling'the incorporated blowing agency, may be performed in any suitable manner preferably however in the spreader process by passing the sheet onto a steam chest and in the calendering process' in the first stages of the curing operation. But however effected it is essential to expel or blow a substantial portion. at least of the incorporated fluid out of the sheet before the plastic sets or hardens. All need not be expelled at this time. Care must be exercised to guard against case orfskin hardening, i. e. surface setting, before the porosity has been adequately "developed. The porosity develops in the first few minutes and is usually complete in about'ten minutes even when water is used.

When the spreading method is followed expulsion of the incorporated fluid occurs on the steam chest (if used) and necessitates careful manipulation ,of. the sheet in getting it into a heater, if the plastic is vulcanizable.

' If the plastic is not vulcanizable, the sheet plastic is vulcanizable this may take place in a room at ordinary temperature or higher, or in ashoe-type of heater, or in open steam, or while the sheet is buried in talc, orin any other suitable manner, depending of course 1 upon the curatives employed and the pressuit it. It is also advisable to set the sheet while free of substantial mechanical pressure so as not to alter its porosity, but a mild mechanical pressure not preventing a substantial escape of trapped air or vapor may be used particularly with incorporated liquid such aswater where the composition and thickness of the stock porosity is not sought.

The preferred plastic is a vulcanizable rubber composition and quick curing (that is to say, curable in a short time of twenty tothirty minutes, at. a temperature of not more than200 F. and preferably less). But vulcanizable rubber compositions in general, not quick curing, maybe employed. In its broadest aspects the invention, however, is not limited to rubber compositions but includes'plastics that may be set in a permanently pliable condition. An example of a suitable pyroxylin compound has been given which may be rendered porous after the underlying principle in this invention.

' Broadly, the invention comprehends the use'of any suitable fluid for obtaining porosity. WVater, air and. gas have been mentoned. But any liquidnon' solvent of the plastic and having a high vapor pressure, such as alcohol or aqueous solutions vaporizable at certain different degrees of'tempermits and a high perature, may beemployed so long as the substance in'solution does not deleteriously modify the action of other ingredients in the compound selected. The porosity of the product varies with the composition ofthe batch both as to' proportions, nature and amount of the ingredients particularly of course the plasticbinder and fibers; By the methods of manipulation the product is also effected but experience in a short time will enable this factor to be controlled. The easiest way to regulate the degree of porosity is to vary the amount of incorporated pore producing agent and of the various ones mentioned water is the best.

Solvent naptha, that is'the distillate of coal tar having a boiling point between 300 and 400 F is the preferred softening agent as it facilitates incorporation of fibers on the mill or in a mixer in the formationfof a calenderable mass, and permits mechanical working of quick-curing rubber compounds. but any of the so called solvents or softeners of rubber appear to be equivalents of'the solvent naptha in that they soften; the coal tar hydrocarbons such as benzol, toluol, xylol,

napthalene, anthracene, or anthracene oil and the aliphatic hydrocarbons chiefly .p'e-' troleum products such as naptha, gasoline or kerosene oil. The softening agent also assists in obtaining porosity.

The preferred filler material is cotton fibers, such as may be derived by grinding fibers will be ground before incorporation into the plastic but to a certain extent the mixing operations may be relied upon to reduce the fibers tothe proper state of fineness. Other fibrous materials that maybe satisfactorily used are mechanical wood pulp, chemical Wood pulp, newspaper, cotton'linters, and hull fibers. Any vegetable or animal fiber. is apparently available.

The thickness of the sheet product having the desirable breathing property may be varied widely, porosity having been obtained in the calendering method and using water, in a sheet as much as one-halt an inch thick. Ordinarily. however, the sheet product will be comparatively thin, it a backing is an ployed about twice the thickness of the tabric alone, and in the case of insole stock about one-sixteenth or an inch thick. The blowing or expulsion of the pore producing agency seems to increase the thickness of the stock.

In the foregoing, it has been endeavored to fully and explicitly disclose the nature of the invention which is believed broadly new. It is to be understood therefore, that the same is not limited to any details not essential to the production of a pliable porous sheet material, and reference should bemade t0 the claims for .an understanding of its scope. v

In the claims the expressions permanently pliable and permanently porous have been usedto denote properties that are retained by the product during its normal life or service and not everlastingly, tor all time.

Having thus described our invention, what we claim and desire to protect by Letters Patent is:

1. An artificial pliable and air-permeable sheet material of plastic-bound unwoven and unfelted fibers.

2. An artificial pliable and air-permeable sheet material of plastic-bound unwoven and unfelted fibers having substantial resistance to abrasion.

3. An artificial pliable air-permeable imitation leather consisting of unwoven and unfelted fibers bound by plastic. and securedto a strain resisting backing. I

4. An artificial air-permeable sheet material consisting of unwoven fibrous material bound by vulcanized rubber composition.

5. An artificial pliable and air-permeable sheet material consisting of unwoven fibrous material bound by vulcanized rubber compo sition and having substantial resistance to abrasive scufiing. 1

6. An artificial pliable and air-permeable sheet material consisting of unwoven fibrous material bound by vulcanized rubber composition and. having substantial resistance to abrasive scufiing and of a hiather-li 'o-grain.

7. An artificial. pliable and air-y rineable sheet material. consisting of u-nwoven fibrous material bound by mlcaniscd rubber. c,om--

position and having substantial resistance to abraslve scufiing and the appearance and feel ofleather adapted to the same kind of service. I l 8. An artificial pliable air-permeable 1mitation leather consisting of fibers bound by vulcanized rubber composition and to a strain-resisting backing; V

,9. A pliable porous sheet material containing fibers and binding vulcanized, rubber composition, the Weight of fibers being not more than 2-3; times the weight of rubber in the composition.

.10. A pliable porous sheet material c0nsisting of fibers embedded in vulcanizedrubber, bound to a fabric backing, and surfaced with nitro cellulose, the whole being airpcrmeable.

1 1. Anartificial air-permeable and permanently flexible sheeted material of unwoven and unfelted fibers bound together by a plastic and substantially non-absorptive of water. f

12. That method of making a permeable sheet material which includes mixinr fibrous and plastic materials and distribut vely inpliable permeable condition.

13. That vmethod of making a permeable sheet material which includes mixing fibrous material andpvulcanizable rubber con iposition and distributively incorporating fluid therein, sheeting :the mix, subjecting the sheet to sufficient heat to gently blow aeriiorm fluidtheretrom and leaveit iorous without con-finingnietal restricting the exit of the fiuicband. finally completely vulcanizing the sheet at a temperature suited to its composition; I r

14:. That method of making a permeable sheet material which includes mixing fibrous and plastictmaterials and distribntively incorporating fluid therein, sheeting the mix onto fabric, gently expelling incorporated fluid with the sheet-substantiallyunconfined by rigid metal members, and finally setting the sheet in a pliable permeable condition.

15. Thatmethod of making a permeable;

sheet material which, includes making a mix of. calender-able consistency of fibrous plastic thickness,

stantially tree of confining metal, and finally setting the sheet in .a pliable and porous zcon dition.

16. That method of making .a permeable sheet material which includes .-niaking :a mix ost calenderable consistency of fibrous mate- :rial and vulcanizable rubber composition and distributively incorporating a blowing agency therein, calendering the mix to form a sheet of the desired thickness, gently expanding and expelling the blowing agency while the sheet is substantially free of confining metal, and finally setting the sheet in a pliable and porous condition.

17. That method of making a permeable sheet material which includes mixing filamentary and plastic materials and distributively incorporating a vaporizable liquid therein, sheeting the mix so as to retain disseminated a substantial portion of the liquid, subjecting the sheet to heat suflicient to expel vapors at least of the liquid, and finally setting the sheet permanently pliable and porous.

18. That method of making a permeable sheet material which includes mixing filamentary material and vulcanizable rubber composition and distributively incorporating a vaporizable liquid therein, sheeting the mix so as to retain disseminated a substantial portion of the liquid, subjecting the sheet to heat sufficient to expel vapors at least of the liquid, and finally setting the sheet permanently pliable and porous.

19. That method of making a permeable sheet material which includes making a substantially uniform and cohesive mix of fibrous and plastic materials and of a liquid non-solvent of the plastic, sheeting the mix so as to retain disseminated a substantial portion of the liquid, subjecting the sheet to heat sufficient to expel vapors at least of the liquid, and finally setting the sheet permanently pliable and porous.

20. That method of making a permeable sheet material which includes making a substantially uniform and calenderable mix of fibrous material and 'vulcanizable rubber composition and of a liquid non-solvent of the rubber, calendering the mix to form a sheet and retaining disseminated a substantial portion of the liquid, subjecting the sheet to heat sufiicient to expel vapors at least of the liquid, and finally setting the sheet permanently pliable and porous.

21. That method of making a permeable sheet material which includes making a subtantially uniform and cohesive mix of fibrous and plastic materials and of Water, sheeting the mix so as to retain disseminated a substantial portion of the liquid, subjecting the sheet to heat suflicient to expel vapors at least of the water, and finally setting the sheet permanently pliable and porous.

22. That method of making a permeable sheet material which includes making a substantially uniform and calenderable mix of fibrous material and vulcanizable rubber composition and of water, rolling out a sheet of the mix so as to retain disseminated a substantial portion of the liquid, subjecting the sheet to heat sufiicient to expel vapors at least of the Water, andfinally setting the sheet permanently pliable and porous.

23. That method of making a permeable sheet material which includes making a calenderable mix of rubber composition, quick curing ingredients, fibers, a softening agent facilitating mixing and calender-ing, and a liquid non-solvent of rubber, calendering out a sheet of the mix, finishing the surface of the sheet as desired, subjecting the sheet to heat so as to expel vapors of the non-solvent liquid and form minute passages therethrough, and finally vulcanizing the sheet completely.

24. That method of making a permeable sheet material which includes making a calenderable mix of materials including rub ber, quick curing igredients, fibers, solvent naphtha and Water, calendering the mix to form a sheet, subjecting the sheet to heat so as to expel vapors of retained water and form pores therethrough, and finally completely vulcanizing the sheet in a porous, pliable and serviceable condition.

25. That method of making a permeable sheet material which includes making a calenderable mix of materials including rubber, quick curing material, fibers, solvent naphtha, and water, calendering the mix onto one or more surfaces of a strain resisting flexible sheet, subjecting the sheet to heat so as to expel vapors of the Water and form pores therethrough, and finally completely vulcanizing the sheet in a porous, pliable and serviceable condition.

26. That method of making a pliable transpiratory sheet material which includes making a sheet of fibrous and plastic materials and incorporating a vaporizable liquid therein, expelling Vapors of the liquid so as to render the sheet porous, and finally setting the sheet in a pliable porous condition.

27. That method of making a permeable and pliable sheet material which includes sheeting co-mingling fibers and plastic materials, and setting the sheet in a porous permanently serviceable condition.

28. That method of making a permeable and pliable sheet material which includes making a porous sheet of fibers and vulcanizable rubber composition, and completely vulcanizing the sheet while porous in a permanently pliable and transpiratory condition.

29. That method of incorporating fibers in a batch of vulcanizable rubber composition which includes, adding to the vulcanizable rubber composition a softening agent reducing its viscosity, and distributively incorporating fibers in the composition while in a softened condition.

Signed at New York, New York, this 25th dav of March, 1921.

WILLIS A. GIBBONS. HERMAN W. BITTER. 

